Desmethyl avermectin compounds wherein one or both of the oleandrose saccharide groups are demethylated are disclosed in Schulman et. al. in The Journal of Antibiotics, 38, 1494-1498 (1985). Such compounds are natural products produced by the fermentation of a strain of Streptomyces avermitilis in the presence of sinefungin. The instant compounds are derivatives of the compounds disclosed in Schulman et. al. Other avermectins missing one or both of the 3'-O- and 3"-O-methyl groups are disclosed in EPO published application 276131, and derivatives of these compounds are also used as starting materials for the compounds of this invention. It is known from Schulman et. al. that such avermectin derivatives missing one or both of the 3'-O- and 3"-O-methyl groups have reduced potency as anthelmintic agents. However certain derivatives obtained through chemical modification of these compounds have highly potent antiparasitic and insecticidal activity.